Quote:
Originally Posted by wwmiv
Those larger diesel trains would be a major safety hazard running on the same tracks without temporal separation, let alone technical and engineering limitations to combining the technologies. That’s why you don’t see that any real world examples of this approach, that I know of. You’d either have to electrify the entire system or require commuter transfers at the edge of a centrally electrified system. Either way, that would require massive investment in the core to integrate the current termini into a functioning system.
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What are you talking about? Any electrification system would be overhead catenary. Diesel trains run under catenary all the time, including
on the South Shore Line right here in Chicago.
Or on the Northeast Corridor in New Jersey. There's no regulatory issue with installing an overhead power system on a diesel road - although freight railroads may want to ensure that double-stack container cars can fit under the wires, and some bridges over the tracks may need to be raised higher.
The temporal separation thing you're thinking of is not about power supply, but about crashworthiness. Most modern multiple-unit trains from foreign manufacturers - like the ones on NJ's RiverLine, or Texas' Cotton Belt - have an efficient, lightweight design to save energy and improve performance. However, FRA historically didn't want lightweight passenger trains running on the same tracks as uber-heavy freights... in the event of a crash, lightweight trains would get wrecked along with everybody inside them. So American commuter rail operators were forced to purchase heavy, inefficient locomotives and cars (whether diesel OR electric) that would hold up better in a freight collision.
BUT - FRA's policy has now changed. The Positive Train Control system being installed across the country drastically reduces the likelihood of crashes, so FRA will now issue waivers to any railroad that wants to run modern lightweight equipment - whether diesel OR electric. Caltrain in SF is currently installing an overhead catenary system AND plans to run modern, lightweight trains AND will mix them with UP freight trains at several points along the corridor.